The extension of membranous processes by cells serves a great variety of purposes during growth and development, and results from extensive, highly regulated, and localized rearrangements of cytoskeletal and membranous elements. The mechanisms that control these rearrangements are poorly understood but appear to rely on the compartmentalization of the intracellular signaling apparatus. Thus I am studying how a cell chooses where on its periphery to initiate a localized morphological change, and how molecules that affect those changes are recruited to that site. As a model, I have been studying a form of process extension, the construction of a membranous pedestal by vertebrate cells in response to the adherence of a pathogenic bacteria Enteropathogenic E. coli (EPEC [1]). An understanding of localized signaling in pedestal formation initiated by EPEC is applicable to a broad range of problems in cell biology including those concerning the migration and cell-cell interactions of epidermal cells. Moreover, the responsible signaling pathways may well be disturbed in cancer cells, including transformed melanocytes, accounting for their motility and invasiveness.